Dual fuel systems supply the combustion chamber of an engine with two different types of fuel. In many cases, one of these fuels will be a liquid such as diesel fuel, and the other will be a gaseous fuel such as natural gas. Such systems often use a dome loaded regulator to control a pressure of the natural gas. This type of regulator is controlled by a reference pressure, for example, a pressure of the diesel fuel. By using a reference pressure, the engine can be supplied with each fuel in the proper pressure ratio.
However, the diesel fuel pressure is subject to fluctuations due to its incompressibility. Fuel pumps and fuel injectors can create fluctuations in this fuel pressure that would typically be passed on to the gaseous fuel pressure, since the diesel fuel pressure serves as the reference for the gaseous fuel pressure. Because the gaseous fuel's density is sensitive to these pressure fluctuations, engine operation may suffer as a result of the fluctuating pressures.
One attempt to address fuel system pressure fluctuations is described in U.S. Pat. No. 7,463,967 issued to Ancimer et al. on Dec. 9, 2008. The '967 patent describes a system that measures gaseous fuel pressure and adjusts fuel injection pulsewidth in order to correct for differences between a target fuel pressure and the measured fuel pressure. This system uses an engine map and calculations performed by an engine controller to modify the injector pulsewidth to a value that is calculated to provide the correct mass of fuel to the engine for a given engine parameter.
While the system of the '967 patent may provide some control over gaseous fuel pressure, it does so with sensors and a controller that are complex and require separate programming. Further, because the system of the '967 patent relies on electronic signals and calculations, there may be an increased potential for error, malfunction, and lag in the control system.
The present disclosure is directed toward one or more of the problems set forth above and/or other problems of the prior art.